1. Field of the Invention
The present invention relates to a tuning fork-type vibrator, a tuning fork-type vibrator manufacturing method, and an angular velocity sensor. In particular, the present invention relates to a tuning fork-type vibrator that includes a base to be supported by a base substrate such as a circuit substrate, and legs extending from the base, and that can be used in an angular velocity sensor, and a method for manufacturing the same.
2. Description of the Related Art
FIG. 13 is a drawing showing an example of a related-art tuning fork-type vibrator. A tuning fork-type vibrator 1 shown in FIG. 13 includes a base 2 and two legs 3a and 3b extending from the base 2. The tuning fork-type vibrator 1 is supported by a substrate 5 with a supporting member connected to the base 2, such as a supporting substrate 4, interposed theretherebetween (see, for example, Japanese Unexamined Patent Application Publication No. 2005-345404).
FIG. 14 is a drawing showing another example of a related-art tuning fork-type vibrator. A tuning fork-type vibrator 1 shown in FIG. 14 includes a base 2 and two legs 3a and 3b extending from the base 2 and is supported by a substrate (not shown) with a supporting member provided in the center of an edge of the base 2, such as a supporting pedestal 6, interposed therebetween (see, for example, Japanese Unexamined Patent Application Publication No. 2004-233288).
FIG. 15 is a drawing showing yet another example of a related-art tuning fork-type vibrator. A tuning fork-type vibrator 1 shown in FIG. 15 includes a base 2 and two legs 3a and 3b extending from the base 2 and is supported by a substrate (not shown) with a pedestal 7 connected to the base 2 interposed therebetween (see, for example, Japanese Unexamined Patent Application Publication No. 2006-208030).
When subjected to the application of a drive signal, any of the tuning fork-type vibrators 1 shown in FIGS. 13 to 15 make basic vibrations at the resonant frequency in drive mode such that the legs 3a and 3b are both opened or closed in a plane having the legs. When a rotation angular velocity is applied about an axis parallel to the longitudinal direction of each tuning fork-type vibrator 1 in this basic vibration state, a Coriolis force is applied to the legs 3a and 3b in opposite directions perpendicular to the directions of the basic vibrations. As a result, the legs 3a and 3b are displaced in the opposite directions. For this reason, the rotation angular velocity can be detected from a signal output from each tuning fork-type vibrator 1 in relation to the displacements of the two legs 3a and 3b thereof. Thus, the tuning fork-type vibrators 1 can be used in an angular velocity sensor.
However, in each of the tuning fork-type vibrators 1 shown in FIGS. 13 to 15, in-plane, in-phase vibrations occur around the resonant frequency in the drive mode. Therefore, these tuning fork-type vibrators are significantly negatively affected by interference between drive vibrations and in-plane, in-phase vibrations. For this reason, if each tuning fork-type vibrator 1 is used, for example, in an angular velocity sensor, basic characteristics of the angular velocity sensor, such as the sensitivity and the offset thereof, are destabilized. In this specification, the phrase “in-place, in-phase vibrations” means that the two legs of a tuning fork-type vibrator vibrate in phase with each other in a location having the two legs, that is, the legs vibrate as directed in one direction simultaneously rather than vibrating such that the legs are both opened or closed.
In addition, each of the tuning fork-type vibrators 1 shown in FIGS. 13 to 15, is supported by a substrate with a supporting member, which is a different member, interposed therebetween. Therefore, the number of members is increased and the cost is increased accordingly.
In particular, the tuning fork-type vibrator 1 shown in FIG. 14 is supported at the center in the width direction, of the base 2. For this reason, the electrode structure that connects the vibrator to a substrate is relatively complicated. Also, since the tuning fork-type vibrator 1 is supported at the center thereof using a structure that directly connects the vibrator to a substrate, it is difficult to control the mounting of the tuning fork-type vibrator, the application of an adhesive, and other assembly processes, and the cost is increased accordingly.